Mid-infrared spectrometry: A tool for the determination of chemical parameters in Emmental cheeses produced during winter

Abstract

The study investigates the potential use of the mid-infrared (MIR) spectroscopy in transmission mode for determining some chemical parameters of European Emmental cheeses. A total of 91 Emmental cheeses produced during the winter in Austria (n = 4), Finland (n = 6), Germany (n = 13), France (n = 30) and Switzerland (n = 38) were investigated. Fat, total nitrogen (TN), water-soluble nitrogen (WSN), non-protein nitrogen (NPN), sodium chloride (NaCl) and pH were analysed by the reference methods. The MIR transmission of different cheeses was also measured by a Nicolet Magna 750 IR spectrometer in a measurement range of 4000-600 cm-1. Partial least square analysis together with the leave-one-out cross-validation technique was used to develop calibration models for different cheese parameters. The best results for NPN (R2 = 0.85; ratio of standard deviation to root mean square error of prediction (RPD) = 2.58), pH (R2 = 0.82; RPD = 2.34), WSN (R 2 = 0.80; RPD = 2.26), NaCl (R2 = 0.70; RPD = 1.91), fat (R2 = 0.69; RPD = 1.87), TN (R2 = 0.62; RPD = 1.60), WSN/TN (R2 = 0.83; RPD = 2.81) and WSN/NPN (R2 = 0.57; RPD = 1.52) were obtained when the spectra were subjected to the first derivation and smoothing after maximum normalisation. It can be concluded that MIR-transmission spectroscopy can be considered as a suitable technique for the prediction of NPN, pH, WSN and WSN/TN of European Emmental cheeses with different origins. The NaCl, TN, WSN/NPN and fat can also be estimated, but with much lower precision. © INRA, EDP Sciences, 2005.